<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		圆的半径：<input type="text" id="input1" />
		<button onclick="calc()">计算</button>
		
		<script>
			
			console.log("π="+Math.PI);
			
			function calc()
			
			{
				var r =parseFloat(input1.value)
				var area = Math.PI * r * ;
				alert("圆的面积:"+area);
			}
			console.log(Math.abs(-10));
			console.log(Math.round(4.4));
			console.log(Math.round(4.5));
			console.log(Math.ceil(4.5));
			console.log(Math.floor(4.5));
			console.log(Math.pow(2,10));
			console.log(Math.sprt(16));
			console.log(Math.random());
			console.log(Math.floor(Math.random()*10+1));
			console.log(Math.floor(Math.random()*3+1));
			 
		</script>
		
		
		
	</body>
</html>
